Apparatus for detecting imperfections on a web

ABSTRACT

The imperfections on a moving web are detected by optical means. A plurality of photoconductive elements are arranged laterally with respect to the advancing direction of the web. The photoconductive elements are reciprocated together in one direction parallel to the direction in which the photoconductive elements are arranged.

United States Patent Inventor Fumio Sugaya Kanagawa, Japan Appl. No.802,947 Filed Feb. 27, 1969 Patented June 29, 1971 Assignee Fuji PhotoFilm Co., Ltd.

Kanagawa, Japan Priority Feb. 27, 1968 Japan 43/ 1 1960 APPARATUS FORDETECTING IMPERFECTIONS ON A WEB 3 Claims, 5 Drawing Figs.

US. Cl 356/199, 250/219, 356/200, 356/238, 356/239 Int. Cl G01n 21/18,GOln 21/30,G01n 21/16 Field of Search 356/72,

[56] References Cited UNITED STATES PATENTS 2,686,452 8/1954 Bentley250/228 x 3,134,021 5/1964 Ploke 356/225 X RE25,671 10/1964 Larew et al.356/199 X 3,157,915 11/1964 Gilbo 356/199X 3,206,606 9/1965 Burgo et a1.356/200 X 3,410,643 1 1/1968 Jorgensen 356/200 3,479,518 11/1969Akamatsu et a1. 356/200 X 3,495,089 2/1970 Brown 356/199 X FORElGNPATENTS 79,613 1 1/1962 France 356/199 Primary Examiner-Rona1d L. WibertAssistant Examiner-Warren A. Sklar AltorneySughrue, Rothwell, Mion, Zinn& MacPeak ABSTRACT: The imperfections on a moving web are detected byoptical means. A plurality of photoconductive elements are arrangedlaterally with respect to the advancing direction of the web. Thephotoconductive elements are reciprocated together in one directionparallel to the direction in which the photoconductive elements arearranged.

PATENIEU 29197] sum 1 UF 2 FIG. 2

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INVENT OR FUMIO SUGAYA ATTORNEYS PATENTEUJUNZSIBH 8,589,816

SHEET 2 OF 2 INVENTOR FUMIO SUGAYA ATTORNEYS.

APPARATUS FOR DETECTING IMPERFECTIONS ON A WEB BACKGROUND OF THEINVENTION l. Field of the Invention The present invention relates to anapparatus for detecting imperfections on a moving web by optical means,and in particular to an apparatus for detecting imperfections on amoving web where the arrangement of a plurality of photoconductiveelements is reciprocated together in one direction.

2. Description of the Prior Art l-Ieretofore, there have been threetypes of apparatus for detecting imperfections in a web. In general,they employ the use of reflected and transmitted light. The three typesare as follows: a type in which a number of photoconductive elements arearranged laterally and adjacent to the advancing web, a type called the"flying spot method" in which a light spot is swept in the efi'ectivesite field of the photoconductive element, and a type called the flyingimage method in which the portion to be detected is uniformlyilluminated at a point thereon which corresponds to the site field ofthe photoconductive element is swept. The first type in which aplurality of I photoconductive elements are arranged laterally andadjacent to the advancing web is simple in construction and durable,

but generally, it is difficult to detect imperfections such as scratchesextending parallel to the direction in which the web is advancingbecause the signal is AC amplified. On the other hand, the third typecalled the flying image method" is effective for continuousimperfections such as scratches extending parallel to the web-advancingdirection, but it is necessary to make the scanning speed extremelylarge in order not to miss the scanned portion between successivescannings. Accordingly, the third type requires a complex and largeapparatus.

SUMMARY OF THE INVENTION In accordance with the present invention, thereis provided a novel detecting apparatus which has the advantages presentin the conventional types of detecting apparatus which are set forth asthe first and third types above, but with none of the disadvantageswhich are found in those conventional types of detecting apparatus.

A number of photoconductive elements having separate fields of view arearranged laterally with respect to the advancing direction of the weband are reciprocated together in the direction of their arrangement atthe definite amplitude and period. Thus, all of the imperfections,including the ones continuously extending in the advancing direction ofthe web, are detected.

It is an object of the present invention to provide an apparatus fordetecting imperfections effectively.

It is another object of the present invention to provide an apparatusfor detecting imperfections on a moving web by employing a plurality ofphotoconductive elements which are reciprocated laterally.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a perspective view partly cutaway showing an embodiment of the detecting apparatus in accordance withthe present invention.

FIG. 2 is a cross-sectional side view partly broken showing thedetecting portion of the detecting apparatus in accordance with thepresent invention.

FIG. 3 is an enlarged sectional view showing another embodiment of thephotoconductive elements provided at the detecting portion of thedetecting apparatus in accordance with the present invention.

FIG. 4 is an enlarged sectional view of the detecting portion of thepresent invention.

FIG. 5 is an electric circuit diagram employed in accordance with thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 showingan embodiment of the present invention, the reference character Idenotes a lamp housing having a tubular lamp 2 therein. A filter 3 isprovided at a window disposed at the bottom of the lamp housing I. Thefilter 3 is an infrared transparent filter to be used fora web ofphotosensitive material such as photographic film, and is not necessaryfor every web used in the present invention. The light passing throughthe filter 3 is irradiated onto the web 4. The web 4 is tensioned in itshorizontal position by rollers 5 and 6.

Under the web 4 there is provided a slit 7. Under the slit 7, there ispositioned a reciprocating support 8 carrying a plurality ofphototransistors D5D84 thereon. The reciprocating support 8 is suspendedby a pair of springs 9 and 10 in the horizontal position. One end of thereciprocating support 8 is connected to a coil l2 of a vibrator llprovided at the end of the reciprocating support 8. By connecting analternating current source of approximately eight cycles per second withthe coil l2, the reciprocating support is reciprocated or vibrated inthe horizontal direction. The output of the respective phototransistorsis taken out through a cable 13 containing soft thin lead wires. Thereis another cable 13' on the opposite side though not shown in thedrawing.

Referring now to FIG. 2 there is shown in detail the detecting-portionof the detecting apparatus in accordance with the present invention. Aplurality of phototransistors D1D4 and D'D88 are provided on theopposite ends adjacent the reciprocating support 8. The above-describedphototransistors DlD4 and D85-D88 (not shown) are secured to a fixedsupport and serve to detect the near edge portions on the opposite sideof the web 4 irrespective of the location of the other phototransistorsD5D84 on the reciprocating support 8. The fixed phototransistors D1-D4and D85-D88 detect only light value variations which have a shorterperiod than the reciprocating period of the reciprocating support 8. Theimperfections having a longer period of light value variation than theperiod of reciprocation of the reciprocating support 8 are detected bythe phototransistors DS-D84 arranged on the reciprocating support 8.

The light value transmitted through the web 4 is constant if the web 4is normal and has no imperfections, but varies if the web 4 has anyimperfection. Imperfections on the web are detected by variations in thetransmitted light value received. However, as in the present embodiment,if the web 4 is half transparent, the light transmitted through the webis scattered and it becomes difficult to detect the variationeffectively by the photoconductive elements 8 disposed under the web. Inthis respect, the photoconductive elements 8 employed in the presentinvention have an individual field of view which does not receive thescattered light but only the transmitted light. Thus, thephototransistors 8 provided in accordance with the present invention candetect the imperfections even of a semitransparent web.

Although phototransistors are employed in the above describedembodiment, it is apparent that other photoconductive elements having arelatively large field of view can be employed if optical lenses l4 areadapted thereto as shown in FIG. 3. The fields of view adjacent to eachother are overlapped to some extent.

The amplitude of movement of the reciprocating support 8 is preferred tobe more than twice as long as the distance between two adjacentphototransistors. Uniform sensitivity cannot be achieved for everyimperfection at every position on the web, unless the phototransistorscans the imperfection at a speed greater than a minimum speed.

FIG. 5 illustrates a part of the electric circuit for recognizing andjudging the signals taken out of the cables I3, 13'.

In the present embodiment of the invention, 88 phototransistors areprovided. 80 of them, with the exception of the eight fixedphototransistors DID4 and D85-D88, are divided into eight channels. Eachchannel has l phototransistors. The residual phototransistors Dl-D4,

D85-D88 are included in the opposite end channels. One

channel, of the channels present is illustrated in FIG. 5.

In the circuit of FIG. 5, the signal from the phototransistors isamplified through amplifiers l6, l6 and then transmitted to high passfilters l7, l7 and low-pass filters l8, 18. The output of amplifiers l6,l6 includes a single imperfection signal, whereas, the output of thehigh and low-pass filters includes a continuous imperfection signal.

These signals are regarded as the imperfection signals if the signalsbecome larger than a definite level in the positive and negativedirection. The recognition of the level is carried out by the diodes 20,21, 28, 29, resistors 24, 25, 38, 39, and amplifiers 22, 23, 31, 32. Thelevel is determined by the potentiometers 26, 27, 35, and 36. The signalfrom the amplifiers 22, 23, 31, 32 is transmitted to a recorder 6]together with a signal from the amplifiers 62, 63, etc., in the otherchannel. This signal may be transmitted to a memorizing device capableof driving a marking device for marking the existence of theimperfections on the web, or the memory device can drive a solenoid fortaking out the portion of the web containing the imperfections where thefeeding device has a cutter attached to it.

The electric circuit described hereinabove, also contains a resistor l9which is connected with resistors 55, 56, etc., from another channel anda resistor 30 is connected with resistors 58, 59, etc., from anotherchannel. The signals from all the phototransistors are collected bytheir connection to lines 37 and 46. By the above-described electriccircuit, a continuous imperfection extending laterally with respect tothe advancing direction of the web cannot be detected independently,although a single imperfection and a continuous imperfection extendinglongitudinally can be detected. However, by collecting the signals ofall the elements as described above, the imperfections extendinglaterally can also be detected.

In accordance with the present invention as described, the scatteredlight is not received so that the imperfections in the semitransparentweb can be detected by the transmitting method. This is because therespective photoconductive elements have definite fields of view. Threetypes of imperfections in the web can be detected and distinguished fromeach other by the unique circuit set forth above, they are: a singleimperfection, a continuous imperfection extending longitudinally, and acontinuous imperfection extending laterally.

Since the fields of view of adjacent photoconductive elements are notseparate but do overlap on the web surface, all areas of the web arescanned if the scanning speed is not too high. Moreover, there is nopart in the apparatus which has excessive force exerted on it so thatthe construction of the apparatus can be simple and durable.

Whatl claim is:

l. An apparatus for detecting imperfections on a longitudinally movingweb which comprises:

a. a plurality of photoconductive elements positioned below said web,

b. means for reciprocating said photoconductive elements laterally tothe longitudinal advancing direction of said moving web,

c. a light source disposed on the side of said web opposite from that ofsaid photoconductive elements,

d. shielding means positioned between said web and said photoconductiveelements and including a laterally extending slot aligned with andoverlying said laterally moving photoconductive elements,

e. individual lenses for each photoconductive element overlying saidphotoconductive elements and positioned between said photoconductiveelements and said web for sharply focusing the imperfections of the webwithin the limited fields of view of each of said underlyingphotoconductive elements, and f. an electric circuit responsive to theoutput of said c. a light source disposed on the side of said webopposite that of said photoconductive elements,

d. shielding means positioned between said web and said photoconductiveelements including a laterally extending slot aligned with and overlyingsaid laterally moving photoconductive element,

e. additional photoconductive elements fixedly mounted to a support soas to be fixed relative to said moving web and to said reciprocatingphotoconductive elements and adjacent to said reciprocatingphotoconductive elements for detecting imperfections at the edges ofsaid web during reciprocation of said moving photoconductive elements,and

f. an electric circuit responsive to the output of said photoconductiveelements for indicating the presence of an imperfection in said movingweb.

3. The apparatus for detecting imperfections on a web as defined inclaim 1, wherein said laterally reciprocating photoconductive elementsconstitute a first row, and said apparatus further includes additionalphotoconductive elements stationarily mounted parallel to said movingphotoconductive elements at opposite ends of the path of movement of thesame and constituting a second and fixed parallel row for detectingimperfections at the edges of said longitudinally moving web.

1. An apparatus for detecting imperfections on a longitudinally movingweb which comprises: a. a plurality of photoconductive elementspositioned below said web, b. means for reciprocating saidphotoconductive elements laterally to the longitudinal advancingdirection of said moving web, c. a light source disposed on the side ofsaid web opposite from that of said photoconductive elements, d.shielding means positioned between said web and said photoconductiveelements and including a laterally extending slot aligned with andoverlying said laterally moving photoconductive elements, e. individuallenses for each photoconductive element overlying said photoconductiveelements and positioned between said photoconductive elements and saidweb for sharply focusing the imperfections of the web within the limitedfields of view of each of said underlying photoconductive elements, andf. an electric circuit responsive to the output of said photoconductiveelements for indicating the presence of an imperfection in said movingweb.
 2. An apparatus for detecting imperfections on a longitudinallymoving web which comprises: a. a plurality of said photoconductivepositioned below said web, b. means for reciprocating saidphotoconductive elements laterally to the longitudinal advancingdirection of said moving web. c. a light source disposed on the side ofsaid web opposite that of said photoconductive elements, d. shieldingmeans positioned between said web and said photoconductive elementsincluding a laterally extending slot aligned with and overlying saidlaterally moving photoconductive element, e. additional photoconductiveelements fixedly mounted to a support so as to be fixed relative to saidmoving web and to said reciprocating photoconductive elements andadjacent to said reciprocating photoconductive elements for detectingimperfections at the edges of said web during reciprocation of saidmoving photoconductive elements, and f. an electric circuit responsiveto the output of said photoconductive elements for indicating thepresence of an imperfection in said moving web.
 3. The apparatus fordetecting imperfections on a web as defined in claim l, wherein saidlaterally reciprocating photoconductive elements constitute a first row,and said apparatus further includes additional photoconductive elementsstationarily mounted parallel to said moving photoconductive elements atopposite ends of the path of movement of the same and constituting asecond and fixed parallel row for detecting imperfections at the edgesof said longitudinally moving web.